The present invention relates to an audible traffic signal adding apparatus for visually impaired persons and, more particularly, to an audible traffic signal adding apparatus for visually impaired persons which navigates a visually impaired person crossing a crosswalk by outputting a predetermined sound for a period during which pedestrians are allowed to cross the crosswalk.
In general, analytical studies until now show that when a visually impaired person crosses a crosswalk, he/she performs tasks like those shown in FIG. 10.
FIG. 10 shows a series of tasks required to cross a crosswalk.
FIG. 10 shows a case without any audible traffic signal adding apparatus for visually impaired persons.
First of all, the visually impaired person confirms the existence of the crosswalk (step 101), and then confirms the entrance of the crosswalk (step 102) and the direction in which the person should cross (step 103).
The visually impaired person then estimates the length of the crosswalk (step 104), determines from the surrounding conditions that he/she can cross the crosswalk, and starts crossing the crosswalk (step 105).
The visually impaired person corrects his/her path while crossing the crosswalk (step 106). When the visually impaired person confirms that he/she has arrived at the opposite side of the crosswalk (step 107), he/she corrects his/her position, confirms a direction to go (step 108), and starts walking in the direction, thereby leaving the intersection (step 109).
On some crosswalks, audible traffic signal adding apparatuses for visually impaired persons are installed. Such an apparatus is designed to support a visually impaired person crossing a crosswalk by outputting predetermined sounds to the visually impaired person for a period synchronized with a blue signal for a pedestrian traffic signal i.e., a period during which crossing is permitted.
FIG. 11 shows a series of tasks required for a visually impaired person to cross a crosswalk with an audible traffic signal adding apparatus for visually impaired persons.
A description of the same steps as those in FIG. 10 will be omitted.
As preparations for crossing, steps 101 to 104 are executed as in the above case, and the visually impaired person starts crossing the crosswalk in accordance with a sound output indicating the permission of crossing and output from the audible traffic signal adding apparatus for visually impaired persons (step 105).
In step 106, when the visually impaired person is to correct his/her path while crossing the crosswalk, he/she repeatedly performs the following two tasks: discriminating the front and rear sound sources from the sound pressures (volumes) of predetermined sounds output from the two ends of the crosswalk or the output sequence of the alternately output sounds (step 111) and locating the target sound source positioned in the crossing direction, thereby determining his/her route (step 112).
Conventionally, such an audible traffic signal adding apparatus for visually impaired persons outputs sounds by the method shown in FIG. 12.
FIG. 12 shows the operation of the conventional audible traffic signal adding apparatus for visually impaired persons.
In this case, identical sounds, i.e., sounds 51 and 52 " cu-ckoo", are alternately output from two speakers (sound output means) 50A and 50B opposed/disposed at two ends (start and end points) of a crosswalk.
In this conventional audible traffic signal adding apparatus for visually impaired persons, however, since identical sounds are alternately output from the two speakers opposed/disposed at the two ends of the crosswalk, the two sounds have no sound pressure difference near the middle of the crosswalk. This makes it difficult to discriminate the sounds.
FIG. 13 explains the relationship between the crossing distance and the sound pressure difference.
The sound pressures of sounds output from the speakers 50A and 50B decrease with an increase in crossing distance.
Near the middle of the crosswalk, therefore, the sound pressures of the two sounds become almost equal to each other, and the two sounds have no sound pressure difference.
As described above (see FIG. 11), the visually impaired person discriminates the target sound while crossing the crosswalk in accordance with the sound pressure difference between the two sounds.
More specifically, at the start of crossing, the visually impaired person determines that the sound source having a lower sound pressure is the sound source at the end point (i.e., the target sound source), and also memorizes the output sequence of this sound and the sound having a higher sound pressure and output from the sound source at the start point, which are alternately output.
During crossing, the visually impaired person discriminates the target sound source on the basis of the sound pressure difference between the two sounds and the memorized output sequence, and takes his/her route to the target sound source.
If, therefore, the visually impaired person is confused about the output sequence of sounds owing to an accident or ambient noise at the position where the sound pressure difference between the two sounds becomes almost zero, the visually impaired person has difficulty in locating the target sound source. This makes it difficult to smoothly cross the crosswalk.